Smashed windows are seen at Comerica Bank on July 15, 2013 in Oakland, Calif.

Photo: Demian Bulwa, The Chronicle

Smashed windows are seen at Comerica Bank on July 15, 2013 in...

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A man records the march as hundreds of protesters upset with the verdict in the trial of George Zimmerman marched in downtown Oakland, Calif., on Monday, July 15, 2013, after Zimmerman's acquittal the previous Saturday on charges in the death of Trayvon Martin.

Photo: Carlos Avila Gonzalez, The Chronicle

A man records the march as hundreds of protesters upset with the...

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A protester is led away on an I-880 off ramp near Franklin Street on July 15, 2013 in Oakland California. Riots of varying size have occured in the area for the past three nights since George Zimmerman was found not guilty in the killing of Trayvon Martin.

Photo: Tamara De Jong

A protester is led away on an I-880 off ramp near Franklin Street...

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Protesters march along Harrison Street along Lake Merritt in Oakland on the third night of protests and marches for hundreds of people upset with the verdict in the trial of George Zimmerman on Monday, July 15, 2013, after Zimmerman's acquittal the previous Saturday on charges in the death of Trayvon Martin.

Photo: Carlos Avila Gonzalez, The Chronicle

Protesters march along Harrison Street along Lake Merritt in...

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Dylan Hunter of Oakland and Crystal Conway of Houston, show their support for the hundreds of protesters upset with the verdict in the trial of George Zimmerman as they marched in downtown Oakland, Calif., on Monday, July 15, 2013, after Zimmerman's acquittal the previous Saturday on charges in the death of Trayvon Martin.

Photo: Carlos Avila Gonzalez, The Chronicle

Dylan Hunter of Oakland and Crystal Conway of Houston, show their...

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A car with a smashed windshield on the marchroute as hundreds of protesters upset with the verdict in the trial of George Zimmerman marched in downtown Oakland, Calif., on Monday, July 15, 2013, after Zimmerman's acquittal the previous Saturday on charges in the death of Trayvon Martin.

Photo: Carlos Avila Gonzalez, The Chronicle

A car with a smashed windshield on the marchroute as hundreds of...

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A protester carries a sign along Lake Merritt as hundreds of people upset with the verdict in the trial of George Zimemrman marched in downtown Oakland, Calif., on Monday, July 15, 2013, after Zimmerman's acquittal the previous Saturday on charges in the death of Trayvon Martin.

Photo: Carlos Avila Gonzalez, The Chronicle

A protester carries a sign along Lake Merritt as hundreds of people...

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A movie poster advertising "Fruitvale Station," film about the Oscar Grant killing was vandalized in a downtown bus shelter Monday July 15, 2013. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

Photo: Brant Ward, The Chronicle

A movie poster advertising "Fruitvale Station," film about the...

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On Telegraph Avenue in downtown Oakland, the graffiti was still apparent Monday July 15, 2013. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

Photo: Brant Ward, The Chronicle

On Telegraph Avenue in downtown Oakland, the graffiti was still...

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Awaken Cafe owner Cortt Dunlap explained that there are bigger issues than a broken window and he put a sign in his window calling for justice and stronger gun laws Monday July 15, 2013. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

Photo: Brant Ward, The Chronicle

Awaken Cafe owner Cortt Dunlap explained that there are bigger...

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A passerby stopped to read the message in the Awaken Cafe window Monday July 15, 2013 broken by protesters two times. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

Photo: Brant Ward, The Chronicle

A passerby stopped to read the message in the Awaken Cafe window...

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Messages in support of Trayvon in a downtown Oakland business Monday July 15, 2013. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

Photo: Brant Ward, The Chronicle

Messages in support of Trayvon in a downtown Oakland business...

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A broken window at a downtown drug store Monday July 15, 2013. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

Photo: Brant Ward, The Chronicle

A broken window at a downtown drug store Monday July 15, 2013. In...

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A front window at the Awaken Cafe was broken twice by protesters prompting a sign in the window from management Monday July 15, 2013. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

Photo: Brant Ward, The Chronicle

A front window at the Awaken Cafe was broken twice by protesters...

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A "Boycott Florida" campaign broke out on Broadway Monday July 15, 2013. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

Photo: Brant Ward, The Chronicle

A "Boycott Florida" campaign broke out on Broadway Monday July 15,...

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Oakland official Juno Thomas (left) explained to Natalie Nadimi how the city could help with her broken windows at Oaklandish, but Nadimi kept asking where the police were Monday July 15, 2013. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

At the Awaken Cafe, diners worked on their computers as the vandalism was apparent on Broadway Monday July 15, 2013. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

Photo: Brant Ward, The Chronicle

At the Awaken Cafe, diners worked on their computers as the...

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A bus shelter featuring a movie poster for "Fruitvale Station," the film about the Oscar Grant killing was vandalized Monday July 15, 2013. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

The Wells Fargo bank had many plywood windows Monday July 15, 2013. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

Photo: Brant Ward, The Chronicle

The Wells Fargo bank had many plywood windows Monday July 15, 2013....

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Dogwood restaurant on Telegraph Avenue was vandalized and has a Trayvon Martin flyer in the window. In downtown Oakland, Calif. many businesses had plywood on their storefronts and broken glass as merchants cleaned up after a weekend of protest and vandalism over the Trayvon Martin verdict.

Photo: Brant Ward, The Chronicle

Dogwood restaurant on Telegraph Avenue was vandalized and has a...

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A protester wearing a death mask listens to speakers as hundreds of people upset with the verdict in the trial of George Zimemrman gathered at Frank Ogawa Plaza and then marched in downtown Oakland, Calif., on Sunday, July 14, 2013, after Zimmerman's acquittal the previous night on charges in the death of Trayvon Martin.

Photo: Carlos Avila Gonzalez, The Chronicle

A protester wearing a death mask listens to speakers as hundreds of...

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Hundreds of people upset with the verdict in the trial of George Zimemrman marched on Broadway in downtown Oakland, Calif., on Sunday, July 14, 2013, after Zimmerman's acquittal the previous night on charges in the death of Trayvon Martin.

Photo: Carlos Avila Gonzalez, The Chronicle

Hundreds of people upset with the verdict in the trial of George...

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A worker removes the smashed out windows at Dogwood on Telegraph Avenue after protesters set fires and vandalized stores in downtown Oakland.

A worker removes the smashed out windows at Dogwood on Telegraph...

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A woman spray paints Trayvon Martin's name in Oakland, California, Sunday, July 14, 2013, after learning that George Zimmerman was found not guilty in the shooting death of Trayvon Martin. (Anda Chu/Bay Area News Group/MCT)

Photo: Anda Chu, McClatchy-Tribune News Service

A woman spray paints Trayvon Martin's name in Oakland, California,...

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Workers board up windows at Flora restaurant in downtown Oakland.

Workers board up windows at Flora restaurant in downtown Oakland.

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Protesters block traffic on Broadway and 14th Street in Oakland on Sunday, a day after George Zimmerman's not guilty verdict in Trayvon Martin's killing.

(07-16) 06:50 PDT OAKLAND -- Protesters outraged at the acquittal of George Zimmerman in Florida briefly blocked a freeway in downtown Oakland and tried to get on a second freeway Monday night in the city's third demonstration in as many days.

Dozens of protesters walked onto northbound Interstate 880 at Broadway about 7:15 p.m., shortly after marching past Oakland police headquarters. Officers led at least one protester in handcuffs off the freeway.

Police removed demonstrators within 15 minutes, and the protesters continued marching downtown, at times blocking motorists and spray-painting graffiti on buildings, before continuing near Lake Merritt and trying at about 8:45 p.m. to get onto eastbound I-580, where they were met by police in a skirmish line. They headed back around the lake, but not before some people set off illegal fireworks and burned an American flag.

The crowd eventually headed back to 15th Street and Broadway, and at 10:45 p.m. people smashed windows of a Comerica bank, a Men's Wearhouse store and a vacant retail space. Police rushed in to make arrests, which led to skirmishes between protesters and police. During the chaos, a tear-gas canister was detonated, and officers were the target of rocks and bottles.

As the night wore on, violence grew. About 11 p.m., a masked protester hit a waiter at Flora Restaurant and Bar on Telegraph Avenue in the face with a hammer as he tried to protect the restaurant, whose windows were broken two nights ago.

By night's end, police had arrested six men, two women and a male juvenile, with most of them hailing from outside Oakland, said Officer Johnna Watson, a department spokeswoman. The offenses included assault with a deadly weapon, resisting arrest and vandalism.

It was the third protest of the Zimmerman verdict in the city since Saturday night. In moving quickly, police avoided a repeat of a 2010 rally in which 150 people protesting education budget cuts were arrested for walking onto the same stretch of freeway and shutting it down for an hour.

Merchants clean up

Earlier Monday, Natalie Nadimi smiled politely as an Oakland city official told her that public works crews were boarding up broken windows and picking up debris for free at businesses damaged over the weekend.

Nadimi is the community engagement manager at Oaklandish, a retail shop on Broadway whose clothing celebrates the city. The store had already boarded up two of the four windows smashed Saturday night, and Nadimi had a different concern.

"There weren't really any police out," she said. "Do you know why there weren't any police?"

Juno Thomas, the city's business development coordinator, said police had been downtown that night but also apologized. He said the force was "spread kind of thin" and that officers would be ready for any additional protests "to prevent further damage."

It was one of many stops Thomas made Monday as downtown merchants went through a familiar ritual - picking up the pieces from back-to-back weekend protests, much as they did after Occupy Oakland rallies in 2011 and a series of demonstrations related to the killing of unarmed BART rider Oscar Grant in 2009.

On Saturday night, masked vandals within a crowd of about 150 people started fires, smashed windows of shops and restaurants, slashed car tires, damaged a BART police car and spray-painted "Kill Zimmerman" and antipolice epithets on the Alameda County courthouse and other locations.

At Dogwood, a bar at 17th Street and Telegraph Avenue, some patrons were cut by shattered glass, the owner said. But police made no arrests Saturday night.

Quan blasts vandalism

On Sunday night, several hundred protesters marched through the streets. There were minor reports of vandalism, and police made one arrest. Several journalists, however, including photographers for The San Francisco Chronicle and the Bay Area News Group, were accosted by protesters late in the night near Dogwood, suffering minor injuries.

The vandalism left merchants frustrated. Some said they agreed with protesters that Zimmerman's killing of Trayvon Martin, an unarmed African American teenager, was a tragedy that highlighted racial injustice. But they wondered why people angry at the acquittal would damage local businesses.

Many peaceful protesters were also upset, saying the vandals represented a small percentage of demonstrators and seemed to be focused more on causing damage than fighting for justice.

After its windows were broken Saturday, Dogwood put up a poster with Martin's picture that read, "I am Trayvon Martin and my life matters." At Awaken Cafe on Broadway, owner Cortt Dunlap put a sign over a damaged window reading, "This window will be fixed later today. When will the U.S. Justice System?"

"I think when a local business culture thrives in a community," Dunlap said, "a lot of the social-justice issues that we see in the Trayvon Martin and George Zimmerman case start to go away."

"When you break the windows of restaurants, you're really hurting the economy, and you're hurting the jobs that are being created in the city," Quan said.

Interim Police Chief Sean Whent said Monday that the department didn't realize that deliberations in the Zimmerman case would take place Saturday and didn't expect a verdict "would come in that quickly."

Whent said 50 officers were brought in from throughout the city to augment the eight to 10 officers downtown, and with the limited staffing, it would have been unwise for officers to wade in to arrest vandals in "that kind of crowd."